The lateral forces exerted on the swing arm spindle will oval the tube on the engine cradle, allowing the spindle & swing arm to rock, with the center bold acts as a pivot point. This creates a sloppy rear end and can be felt by grabbing the rear wheel and pushing and pulling side to side.

This mod supports the spindle on both ends, thus eliminating the rocking motion.

An alternative method is to weld nuts to the swing arm tube.

As I had already painted my engine cradle and installed the gearbox and primary, I chose these clamps as a simple bolt on solution.

Initial fitting, here you can also see the oil filter mount.

Pilot hole on the right, final hole on the left.

Assembled with grease, thread locker, and some Permatex #2.

Final installation.

...well almost final. The heads of the adjustment screws hit the swing arm brace, so I turned the heads down, shortened the screws and took the locknuts down to half thickness.

Heinz's instructions specify drilling @ 8 o'clock, this I did, and it is correct..

but it was with the engine on the bench as pictured. When the cradle is installed in the frame the front end sits lower than on a bench, so 8 o'clock becomes 9 o'clock, and 9 o'clock is a problem!

So, when installing: on a bench = 7 o'clock, cradle in frame = drill at 8 o'clock.
Better yet, trim the adjusting screws down so you never have to worry about hitting the swing arm.